Apparatus for sensing precipitation density of sludge in waste water treatment tank and method therefor

A method for sensing precipitation density of sludge in a wastewater treatment tank, comprising:

• moving in which a density sensing unit is allowed to move by a given distance from the upper part to the lower part in a wastewater treatment tank and to stop at a measuring spot in said wastewater treatment tank;
• stabilizing in which said density sensing unit stands by for a set time after the time said density sensing unit stops at said measuring spot;
• and
• measuring in which said density sensing unit measures sludge density at the water level of said measuring spot after said set time is over,
• wherein said moving, stabilizing, and measuring are sequentially repeated until said density sensing unit reaches the last measuring spot in the lower part of said wastewater treatment tank.